The present invention generally relates to a device for warning miners of an unsafe condition existing in mine shafts. More particularly, the present invention relates to an easily and accurately settable device for actuating an alarm system in response to predetermined amounts of movement of the mine ceiling thereby enabling miners to escape the potential danger of a mine shaft collapse.
Devices which alert miners to potential ceiling collapses in underground mines are not new. Indeed, the art is replete with various devices for warning miners of a potential mine collapse, as evidenced by U.S. Pat. Nos. 1,018,328; 1,737,514; 2,692,924; 3,111,655; 3,341,843; 3,594,773; 3,786,503; 3,826,128; 4,097,854; 4,136,556; and 4,156,236. However, a distinct problem associated with these prior mine alert devices is that they are rather complicated to properly position and accurately set in the mine. Additionally, conventional mine alert devices often require engineering supervision or an inordinant amount of technical training to properly install these devices in mine shafts.
However, according to the present invention, there is provided a relatively simple, compact, yet rugged device which can be accurately and reliably set to a predetermined set point with little technical training by the person installing the device. A predetermined variance or movement in the ceiling of the mine shaft will cause the device to actuate an alarm. According to the present invention, therefore, there is provided a device which will warn miners in an underground mine of a potential hazard existing in the mine shaft so that they may seek safety.
The device according to the present invention utilizes a visual indication to accurately set the device so that an alarm will actuate when a predetermined amount of movement is detected in the mine shaft ceiling. The present device contemplates that a set point will be pre-established prior to installation of the device in the mine shaft.
To pre-establish the set point, a mining engineer need only determine the amount of earth movement which would constitute potential hazard. The mining engineer or the like will thus translate this quantum amount of earth movement into the proper set point on the apparatus which is preferably determined by a gap between two opposing electrical contacts or the like. The gap set point of the present device correlates directly into a visual indication, such as, for example, a pressure indication on a pressure gauge. The gap set point is accurately measured by conventional means, such as feeler gauges or the like, and the corresponding visual indication is adequately noted. Thus, all that a person installing the present device need to effect is a reproduction of the noted visual indication in order to accurately set the gap in the predetermined manner. Thus, installing the present device in the mine shaft does not require any technical training or assistance.
Other objects and advantages of the present invention will become more readily understood to the reader upon consideration of the following detailed description of the preferred exemplary embodiment together with reference to the accompanying drawing.